Pocketbook of Useful Formulæ and Memoranda
for Civil and Mechanical Engineers

325 OF ENGINEERING FOBMULÆ. Electrical Formula, by Paget Higgs, LL.D., O.E, and R. S. Bbough—continued. When s = s' ~ <x, n = n' = 1, and f _ F (<O • (w' + </) - F (d) . (w + g) J F (</) - F (d") ‘ ii. By Poggeudorff ’s method : io + w' iii. By Thomson’s method: (Shunt the battery f with shunt s, and take reading through resistance w; remove the shunt, and increase the resistance to w' so that the original deflection is again pro- duced. In the bridge make b = o, x = co ,a = shunt, w = resistance): w' — w f = s - ----- • w + g If we take s = w +'g, then f = to' — w. By condenser or electrometer method: Connect battery with condenser or electrometer electrodes (if with con- denser as in taking discharge), take deflection c?; shuut battery with w, and take d'. iv. By the differential galvanometer (Latimer Clark) : / = w' - 2w. When to = o, f = w'.